[Cryptech Tech] Comments on Alpha board schematics

[Joachim Strömbergson]

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Aloha!

Joachim Strömbergson wrote:
> I would suggest that the ability to turn the entropy source on or off
> is given to the FPGA. (Which of course could expose the control via
> the core API). If the control is done by the CPU or Tamper-MCU, then
> we could easily end up reseeding the CPRNG using only the ring
> oscillator based entropy provider. Having support for turning the
> entropy source off ana on adds quite a lot of complexity in terms of
> warm up times and startup testing vs starvation of RNG output and
> race problems.
> 
> When I look in Rev02, sheet 03 I assumed there would be a control
> signal for this function, but I don't see it. Has it not been
> included?

Sorry for the confusion, That functionality is present on sheet 02.
Suggestion is to connect FPGA_ENTROPY_DISABLE to pin on FPGA.

- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Alltid i harmonisk svängning.
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 Joachim Strömbergson          Secworks AB          joachim at secworks.se
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